1. Field of Invention
The present invention relates to a thin film transistor structure, and more particularly, to a multi-channel thin film transistor structure.
2. Description of Related Art
There are two types of display architectures: passive matrix and active matrix. In general, a thin film transistor (TFT) can be used as a switching element to control each pixel individually in active matrix type displays. A threshold voltage shift of a TFT may occur due to a continuing positive bias stress or a positive bias stress with heavy-duty circle supplied at the TFT gate electrode. The threshold voltage shift may cause a decrease of the source-drain current and quality degradation of displays.
In organic light emitting diode (OLED) displays or polymer light emitting diode (PLED) displays, for example, each pixel has a switching TFT and a driving TFT. The switching TFT is for controlling a timing of supplying an electric current to a light emitting diode. The driving TFT is for supplying an electric current to the light emitting diode. In a driving TFT, interface degradation between a channel layer and an insulating layer may occur when a continuing positive bias stress is supplied at the gate electrode thereof. The threshold voltage shift due to the interface degradation may result in a decrease of the source-drain current and quantity reduction of the displays.
The threshold voltage shift has a serious effect on displays. Therefore, how to provide a thin film transistor structure to reduce the threshold voltage shift is an issue of great consequence.